1. Technical Field
The present invention relates to a technique for converting previously halftoned data and carrying out printing.
2. Related Art
In recent years, with developments in printing technology spreading in every direction, printing is no longer limited to being on paper, but rather there is now also printing on a variety of media such as resin sheets and labels, as well as printing called digital textile printing in which ink is discharged directly onto a cloth to dye a pattern or the like. There has also been usage in processes for manufacturing semiconductors, the coating of glass substrates to form transparent electrodes, and the like.
As such printing technologies have become increasingly differentiated and generalized, a variety of forms for handling print data have also been born. Conventionally, with computer-based or similar design and creation of digital data, the user has operated the computer with the desire to “print”, thereby generating print data which is then outputted to a printer serving as a print apparatus. Because typically computer displays employ the RGB color system, and because the data is handled at a resolution independent of the resolution of the print apparatus, printing entails color-converting RGB data into a color system (typically CMYK) that corresponds to the ink system used for printing, and converting to dot data that is matched to the resolution and gradation values of the print apparatus. The gradation values handled by a print apparatus varies depending on the model of the print apparatus, and are binary when it is only question of whether or not a dot of a specific ink is formed, ternary (none, light dot, dense dot) in a case where a high-/low-concentration ink is used, or quaternary (none, small, medium, large) in a case where small, medium, and large dots can be formed. It shall be readily understood that multi-valued representation (for example, quinary or septenary) is also possible in combinations of high-/low-concentration ink and small/large dots or small/medium/large dots. Additionally, though only dots of the same shape can be formed, techniques of discharging an ink droplet zero to N times at the same position and thereby performing multi-bit representation corresponding to the number of times N have also been proposed and put into practical use.
In any event, on a computer, there needs to be a process for converting multiple-tone image data, in which representation is often with eight bits for RGB each, meaning a total of 24 bits, to dot data of a low gradation value. This process is usually called either a halftone process (halftoning) or a multi-value conversion process. The computer transmits the dot data, which has previously undergone the multi-value conversion process, to a printer serving as a print apparatus, and the printer drives a printing head and carries out printing in conformity with the dot data. There are a variety of types of print apparatuses in existence, such as inkjet printers that discharge ink droplets and page printers that form one page of latent image onto a photosensitive drum to transfer toner, but an inkjet printer is often used in a case where the medium being printed on is cloth, a semiconductor substrate, or the like. This is because a configuration where printing is performed by moving the printing head in a relative manner with respect to these print media is more readily compatible with different types and sizes of medium. Inkjet printers to begin with include not only serial-type printers in which a print head moves in the width direction of the print medium (a main scanning direction), but also line printers provided with a broad print head able to discharge ink across the width direction of the print medium.
The dot data that is outputted to the print apparatus is temporarily stored in the print apparatus, but usually is sequentially updated as the print process proceeds and, when printing is complete, is deleted from the print apparatus. Specific technical fields, however, have the desire for saving and then repeatedly using the dot data that is generated for the print apparatus. When, for example, textile printing is considered, in instances of digital printing, it is not that a large quantity of cloth of the same pattern is made, but rather production would be high-mix low-volume, and conceivably cloth of the same design would be repeatedly printed in accordance with the demand. Similarly, in fields such as semiconductor substrate manufacturing, too, a similar desire would be present in instances of use in high-mix low-volume production. Apparatuses called page composers, for saving such printing dot data and summoning the data as needed to carry out printing, have therefore also been used.
Moreover, auxiliary models that are small-scale or of a different print resolution may be additionally introduced into an environment to which, for example, principal models capable of large-format printing or high-resolution printing have already been introduced, and in such or similar cases there has been a desire to endow the auxiliary models with compatibility with the principal models and be able to print by directly inputting the halftoned result of the principal models without alteration. See, Japanese Laid-open Patent Application No. 2003-224719, Japanese Laid-open Patent Application No. 2002-154246 and Japanese Laid-open Patent Application No. 10-248016, for example.